Research On Injection-seeded Holmium Single-doped Laser

Coherent Doppler Lidar (CDL) which act as the most potential and promisingmethod in atmospheric wind field initiative detection, has become a hot topic in theresearch task.2μm injection-seeded lasers have become the primarily light sourceof CDL due to the outstanding properties, such as eye safety, high reflection ofaerosol particle coefficient, excellent atmospheric transmission feature. In accountof this, this dissertation intends to make efforts on the research of injection-seededholmium single-doped laser to make some contributions to the development ofinjection-seeded2μm laser.Firstly, we introduce the different operating mechanism of2μm solid laser andinvestigation progress in2μm injection-seeded lasers in details, analyze on theadvantages and disadvantages of various2μm injection-seeded laser, and point outthe advantage of single doped Ho injection-seeded laser and the significance indeveloping injection-seeded Ho laser.Based on level translation and energy transfer of2μm single doped Ho laser,the quasi-two-level rate equations of CW and Q-switched Ho laser are given. UsingCW Ho laser quasi two level rate equation model, with Ho:YAG laser as an example,we discuss the laser output characteristics influenced by cavity loss, transmissivityof output mirror, laser crystal temperature and the size of the pump beam. Using theQ-switched rate equation model, we investigate the laser energy extractionefficiency and laser pulse width as well as the main factor of the influence on them.Based on the classical theory of light interaction, the influence by injected seedlaser on the initial light field distribution in the laser resonator is discussed. Theeffect of seed laser frequency detuning on injection locking of lasers is analyzed onthe basis of numerical simulation, and the relationship between the frequencydetuning range and minimum seed injected power is given, as well as the modematching issue of master laser and the slave laser is discussed.According to the different requirements of each component, the single dopedHo master laser, the Q-swathed slave laser and injection coupled system areanalyzed and designed respectively. The theoretical analysis on single longitudinalmode (SLM) achievement employing double F-P etalons is deduced, and the master laser with double F-P etalons suitable for single doped Ho injection-seeded laserwas designed and completed. General design method of ring cavity laser isintroduced. Meanwhile, six mirror asymmetric ring resonator combined with thecharacteristics of Ho crystal was designed to be used in the slave laser in the singledoped Ho injection-seeded system.On the basis of the study above, experiments were conducted to study theHo:YAG injection-seeded laser. The emission characters of Tm,Ho:YAG masterlaser with double F-P etalon was researched. Up to84mW laser output at2090.8nmwas obtained. The Tm,Ho:YAG master laser to meet with the requirements of themaster laser for Ho:YAG injection-seeded laser. Experimentally, the lasingperformance of Ho:YAG slave laser using six symmetric ring cavity structure isanalyzed. Under100Hz pulse repetition rate, the output of frequency-lockedHo:YAG laser was achieved by coupling the SLM seed laser from Tm,Ho:YAGmaster laser with the Ho:YAG slave laser, obtaining output single pulse energy of7.6mJ with pulse width of132ns.Finally, in allusion to the serious energy loss of SLM master laser after injectedin the coupled system, we proposed the technic proposal using the YAP crystalwhich directly produced linear polarization instead of the YAG crystal, and thencarried out experimental study of Ho:YAP injection-seeded seed laser. Under100Hzpulse repetition rate, the output of injected-seeded laser was achieved by couplingthe SLM seed laser from Tm,Ho:YAP master laser with the Ho:YAP slave laser,obtaining output single pulse energy of8mJ with pulse width of151ns.